feat: add support for BSC #68

Job	Run time
check no-default-features	1m 5s
check serde	1m 4s
check std	1m 1s
clippy / optimism	1m 49s
clippy / bsc	1m 49s
test stable --no-default-features	3m 8s
test stable	3m 1s
docs / optimism	1m 39s
docs / bsc	1m 39s
fmt	13s
test stable --features bsc	3m 15s
test stable --features optimism,opbnb	3m 16s
test beta --no-default-features	3m 8s
test beta	3m 11s
test beta --features bsc	3m 18s
test beta --features optimism,opbnb	3m 23s
test nightly --no-default-features	2m 51s
test nightly	2m 45s
test nightly --features bsc	2m 55s
test nightly --features optimism,opbnb	3m 3s
	47m 33s

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